The role of dietary sodium chloride in the pathogenesis of primary hypertension has remained enigmatic. Insight into its possible contribution may be provided in animal studies which have shown that high sodium intake engenders sustained hypertension if, and only if, the subject is concurrently exposed to recurrent behavioral stress. Accordingly, the present project addresses the hypothesis that a high sodium intake will elevate blood pressure in humans, but only under specific lie stress conditions associated with neuroendocrine-mediated effects on sodium regulation. An initial study is being conducted with medical students maintained on a high sodium diet or placebo for two weeks immediately preceding their final exams. Preliminary results show that resting blood pressure increased during the two weeks prior to examinations in subjects on a high sodium diet but not on the placebo. In addition, subjects in the high sodium group reported changes in perceived stress and state anxiety which were significantly correlated with the magnitude of pressure elevation. These results are consistent with the hypothesis that interactions of stress and salt intake have significant effects on long-term blood pressure regulation, and provide a basis for further investigation of mediating physiological and cellular factors.